Written credit in album art is a courtesy not ruled under any law.

The only thing that is ruled under the law is the copyright ownership %'s, publishing, mechanicals, and all that backend good stuff.

So as long as your publishing, contracts, etc are straight no one ever has to "legally" give you written credit in an album.

Where a lot of confusion comes IMO in situations like this is session musicians are considered (work-for-hire). They come in, get paid hourly and own nothing.

Anyone could be treated as a session musician including a "beat maker" if they wanted to.

Many times the issues around "credit" or "stealing" come in the unsaid confusion between a work-for-hire musician and a true collaborator. And oftentimes many people don't discuss what should be happening upfront until after the fact.

And of course the power dynamic also plays a role in the confusion.

Clyde Stubblefield is a perfect exampled of this. He was James Browns drummer and his sound is essential to hip hop breaks but he was a session musician and was paid a day rate and therefore all his ideas/contributions are owned by James Brown and or whomever owns the masters and publishing.

on the flip side Kanye is the best at this. Ironically Che Pope who ran good music for a minute AND was "one of those Miseducation producers" was great about giving pub and credit to damn near everyone in the room during the process.